public class TestBinaryTree {
    static class TreeNode {
        public char val;
        public TreeNode left; //左孩子的引用
        public TreeNode right; //右孩子的引用


        public TreeNode(char val) {
            this.val = val;
        }
    }

    public TreeNode createTree() {

        TreeNode A = new TreeNode('A');
        TreeNode B = new TreeNode('B');
        TreeNode C = new TreeNode('C');
        TreeNode D = new TreeNode('D');
        TreeNode E = new TreeNode('E');
        TreeNode F = new TreeNode('F');
        TreeNode G = new TreeNode('G');
        TreeNode H = new TreeNode('H');

        A.left = B;
        A.right = C;
        B.left = D;
        B.right = E;
        C.left = F;
        C.right = G;
        E.right = H;

        return A;//就是我的根节点
    }


    //前序遍历
    public void preOrder(TreeNode root){
        if (root==null){
            return;
        }
        System.out.println(root.val+" ");
        //递归遍历左子树
        preOrder(root.left);
        //递归遍历右子树
        postOrder(root.right);

    }

    //中序遍历
    public void inOrder(TreeNode root){
        if (root==null){
            return;
        }
        inOrder(root.left);
        System.out.println(root.val+" ");
        inOrder(root.right);
    }

    //后序遍历
    public void postOrder(TreeNode root){
        if (root==null){
            return;
        }
        postOrder(root.left);
        preOrder(root.right);
        System.out.println(root.val+" ");
    }

    // 获取树中结点个数
    public int size(TreeNode root){
        if(root==null){
            return 0;
        }
        int ret =size(root.left)+size(root.right)+1;
        return ret;
    }

    public static int nodSize;
    public void size2(TreeNode root){
        if (root==null){
            return;
        }
        nodSize++;
        size2(root.left);
        size2(root.right);
    }

    /**
     * 求叶子结点个数
     */
    public int getLeafNodeCount(TreeNode root){
        if (root==null){
            return 0;
        }
        if (root.left==null&&root.right==null){
            return 1;
        }
        return getLeafNodeCount(root.left)
                + getLeafNodeCount(root.right);
    }

    /**
     * 获取第k层节点个数
     */

    public int getKLevelNodeCount(TreeNode root,int k){
        if(root==null){
            return 0;
        }
        if (k==1){
            return 1;
        }
        return getKLevelNodeCount(root.left,k-1)+getKLevelNodeCount(root.right,k-1);

    }

    /**
     * 求当前这个二叉树高度
     */

    public int getHeight(TreeNode root){
        if (root==null) {
            return 0;
        }
        int leftHeight =getHeight(root.left);
        int rightHeight = getHeight(root.right);

        return leftHeight > rightHeight ?
                leftHeight+1:rightHeight+1;

    }

    /**
     * 遍历二叉树 找到val所在节点
     */

    public  TreeNode find(TreeNode root,char val){
        if(root==null){
            return null;
        }
        if (root.val==val){
            return root;
        }
        TreeNode ret= find(root.left,val);
        if (ret!=null){
            return ret;
        }

        ret =find(root.right,val);
        if(ret!=null){
            return ret;
        }
        return null;
    }

    /**
     * 翻转二叉树
     */

    public TreeNode invertTree(TreeNode root){
        if (root==null){
            return null;
        }
        if (root.left==null&&root.right==null){
            return root;
        }
        TreeNode tmp=root.left;
        root.left=root.right;
        root.right=tmp;
        invertTree(root.left);
        invertTree(root.right);
        return root;

    }

    /**
     * 平衡二叉树
     */
    public  boolean isBalanced(TreeNode root) {
        if (root == null) return true;

        int leftH = maxDepth(root.left);
        int rightH = maxDepth(root.right);
        boolean b = Math.abs(leftH - rightH) <= 1
                && isBalanced(root.left)
                && isBalanced(root.right);
        return b;
    }

    public int maxDepth(TreeNode root){
        if (root==null){
            return 0;
        }
        int leftHeight=maxDepth(root.left);
        int rightHeight=maxDepth(root.right);
        int leftHeight1 = leftHeight;
        return leftHeight1;
    }

    }

